Preparation of sulfide chain-bearing organosilicon compounds

ABSTRACT

A sulfide chain-bearing organosilicon compound having the average compositional formula:
 
(R 1 O) (3-p) (R 2 ) p Si—R 3 —S—(R 4 —S m ) q —R 4 —S—R 3 —Si(OR 1 ) (3-p) (R 2 ) p 
 
is prepared at low costs and in high yields by reacting a halogen-terminated organosilicon compound having the formula: (R 1 O) (3-p) (R 2 ) p Si—R 3 —S—R 4 —X, and optionally a halide having the formula: X—R 4 —X and/or sulfur with an aqueous solution or dispersion of a polysulfide M 2 S n  or hydrate thereof in the presence of a phase transfer catalyst. R 1  and R 2  are monovalent C 1-4  hydrocarbon groups, R 3  and R 4  are divalent C 1-10  hydrocarbon groups, m has an average value of 2-6, n has an average value of 2-6, p is 0, 1 or 2, q is 1, 2 or 3, X is halogen, and M is ammonium or alkali metal.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2005-285868 filed in Japan on Sep. 30, 2005,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to a sulfide chain-bearing organosilicon compoundhaving an organoxysilyl group at each end and a polysulfide group at acenter of the molecule, which are linked through amonosulfide-containing divalent hydrocarbon group. More particularly, itrelates to a simple and economical method for preparing the sulfidechain-bearing organosilicon compound in an aqueous system using a phasetransfer catalyst.

BACKGROUND ART

Compounds containing alkoxysilyl and polysulfide groups in the moleculeare known. These compounds are utilized as interfacial binders betweeninorganic materials such as silica, aluminum hydroxide, talc and clayand organic materials such as thermoplastic resins, thermosetting resinsand rubber, bonding agents for improving the adhesion of rubber toinorganic substrates, primers and the like.

Also known are various rubber compositions having silica loaded therein.Typical are tire tread-forming rubber compositions characterized by lowheat generation and abrasion resistance. It is known in the art thatcompounds containing alkoxysilyl and polysulfide groups in the molecule,for example, bis-triethoxysilylpropyl tetrasulfide andbis-triethoxysilylpropyl disulfide are effective to compositions of thistype. The inclusion of these compounds, however, is still insufficientto meet the requirements to further improve tensile strength, resilienceand low heat generation.

One approach to improve the requisite properties is found in JP-A2004-018511 (US Application Publication 2003/0236424 or EP 1375504A1)disclosing a compound having the average compositional formula (5):(R¹O)_((3-p))(R²)_(p)Si—R³—S_(m)—R⁴—(S_(n)—R⁴)_(q)—S_(m)—R³—Si(R²)_(p)(OR¹)_((3-p))  (5)wherein each of R¹ and R² is a monovalent hydrocarbon group of 1 to 4carbon atoms, each of R³ and R⁴ is a divalent hydrocarbon group of 1 to15 carbon atoms, m is a positive number having an average value of 1 to3, n is a positive number having an average value of 2 to 4, p is 0, 1or 2, and q is 1, 2 or 3.

As disclosed therein, the organosilicon compound of the averagecompositional formula (5) is prepared by reacting a halogen-terminatedorganosilicon compound of the general formula (6):(R¹O)_((3-p))(R²)_(p)Si—R³—S_(m)—R⁴—X  (6)wherein R¹, R², R³, R⁴, m and p are as defined above, X is a halogenatom, with an anhydrous alkali metal sulfide or anhydrous alkali metalpolysulfide of the general formula (7):M₂S_(r)  (7)wherein M is an alkali metal and r is a positive number of 1 to 4 onaverage, and optionally a halogen-containing compound of the generalformula (8):X—R⁴—X  (8)wherein R⁴ and X are as defined above and/or sulfur.

This method, however, has some drawbacks. While it uses substantiallycompletely anhydrous alkali metal sulfide or alkali metal polysulfide,the drying of alkali metal sulfide or alkali metal polysulfide hydrateis time consuming. Filtration of the salt is necessary. Since the methodnormally uses a reaction solvent, the solvent must be distilled off atthe end of reaction. There remains a need for a method for thepreparation of sulfide chain-bearing organosilicon compounds in a simplestep and at a low cost.

For the preparation of sulfide chain-bearing organosilicon compounds,the use of phase transfer catalysts is also known. This is taught inU.S. Pat. Nos. 5,405,985, 5,468,893, 5,583,245, 6,448,426, JP-A2004-521945 and JP-A 2004-521946. Although these patents relate tomethods for preparing sulfide chain-bearing organosilicon compoundsusing phase transfer catalysts, no reference is made to a sulfidechain-bearing organosilicon compound having an organoxysilyl group ateach end and a polysulfide group at a center of the molecule, which arelinked through a monosulfide-containing divalent hydrocarbon group.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a safe and economicalmethod for preparing in a simple step a sulfide chain-bearingorganosilicon compound which is compounded in rubber for improving thetensile strength, resilience and low heat generation of rubber.

The inventors have discovered that a sulfide chain-bearing organosiliconcompound having the average compositional formula (4):(R¹O)_((3-p))(R²)_(p)Si—R³—S(R⁴—S_(m))_(q)—R⁴—S—R³—Si(OR¹)_((3-p))(R²)_(p)  (4)can be prepared by reacting a halogen-terminated organosilicon compoundhaving the general formula (1):(R¹O)_((3-p))(R²)_(p)Si—R³—S—R⁴—X  (1),and optionally a halogen-containing compound having the general formula(2):X—R⁴—X  (2)and/or sulfur with an aqueous solution or dispersion of a polysulfidehaving the formula (3):M₂S_(n)  (3)or a hydrate thereof in the presence of a phase transfer catalyst. Inthe formulae, each of R¹ and R² is a monovalent hydrocarbon group of 1to 4 carbon atoms, each of R³ and R⁴ is a divalent hydrocarbon group of1 to 10 carbon atoms, m is a positive number having an average value of2 to 6, n is a positive number having an average value of 2 to 6, p is0, 1 or 2, and q is 1, 2 or 3, X is a halogen atom, and M is ammonium oralkali metal. This method is successful in preparing the compound offormula (4) in a simple and safe way, at low costs and in high yieldsbecause it eliminates a need for drying the polysulfide or hydratethereof as the raw material, and uses it in an aqueous solution ordispersion form.

Accordingly, the present invention provides a method for preparing asulfide chain-bearing organosilicon compound having the averagecompositional formula (4), comprising the step of reacting ahalogen-terminated organosilicon compound having formula (1), andoptionally a halogen-containing compound having formula (2) and/orsulfur with an aqueous solution or dispersion of a polysulfide havingformula (3) or a hydrate thereof in the presence of a phase transfercatalyst.

BENEFITS OF THE INVENTION

According to the method of the invention, a sulfide chain-bearingorganosilicon compound having the average compositional formula (4) canbe prepared from a halogen-terminated organosilicon compound and apolysulfide or hydrate thereof in the presence of a phase transfercatalyst without a need for drying the polysulfide or hydrate thereof.The desired product is obtained in high yields and at low costs. Thesulfide chain-bearing organosilicon compound thus prepared, whencompounded in silica-loaded rubber, is effective for improving thetensile strength, resilience and low heat generation of the rubber, ascompared with the prior art known sulfide chain-bearing organosiliconcompounds. It is useful in the industry as an additive to silica-loadedtire rubber compositions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Briefly stated, according to the present invention, a sulfidechain-bearing organosilicon compound having the average compositionalformula (4) is obtained by reacting a halogen-terminated organosiliconcompound having formula (1), and optionally a halogen-containingcompound having formula (2) and/or sulfur with an aqueous solution ordispersion of a polysulfide having formula (3) or a hydrate thereof inthe presence of a phase transfer catalyst.

One starting reactant is a halogen-terminated organosilicon compoundhaving the general formula (1).(R¹O)_((3-p))(R²)_(p)Si—R³—S—R⁴—X  (1)In the formula, R¹ and R² are independently selected from monovalenthydrocarbon groups having 1 to 4 carbon atoms, for example, alkyl andalkenyl groups such as methyl, ethyl, n-propyl, i-propyl, n-butyl,i-butyl, t-butyl, allyl and methallyl, with methyl and ethyl beingpreferred. R³ is selected from divalent hydrocarbon groups having 1 to10 carbon atoms, for example, alkylene, arylene and alkenylene groupsand combinations thereof, such as methylene, ethylene, propylene,n-butylene, i-butylene, hexylene, decylene, phenylene, andmethylphenylethylene, and combinations thereof. Of these, ethylene,propylene and i-butylene are preferred, with propylene being mostpreferred. R⁴ is selected from divalent hydrocarbon groups having 1 to10 carbon atoms, for example, alkylene, arylene and alkenylene groupsand combinations thereof, such as methylene, ethylene, propylene,n-butylene, i-butylene, hexylene, decylene, phenylene, andmethylphenylethylene, and combinations thereof. Of these, propylene,hexylene and decylene are preferred, with hexylene being most preferred.X is a halogen atom such as Cl, Br or I, and preferably Cl or Br. Thesubscript p is equal to 0, 1 or 2, preferably 0 or 1, and mostpreferably 0.

Typical examples of the compound of formula (1) are given below.(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₃—Cl(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₆—Cl(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₈—Cl(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₁₀—Cl(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₆—Br(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₃—Cl(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—Cl(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₈—Cl(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₁₀—Cl(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—Br(CH₃CH₂O)₃Si—CH₂CH(CH₃)CH₂—S—(CH₂)₆—Cl

The phase transfer catalyst used herein is selected from quaternaryonium cations. Examples of suitable quaternary onium cations include,but are not limited to, tetrabutylammonium bromide, tetrabutylammoniumchloride, tetramethylammonium bromide, tetramethylammonium chloride,tetraethylammonium bromide, tetraethylammonium chloride,tetrabutylammonium phosphate, tetrabutylammonium phosphate,tetrabutylammonium sulfate, tetrabutylammonium fluoride,benzyltrimethylammonium bromide, and tetraphenylammonium bromide. Ofthese, tetra-n-butylammonium bromide and tetra-n-butylammonium chlorideare preferred.

Optionally a halogen-containing compound having the general formula (2)is used in admixture with the organosilicon compound of formula (1).X—R⁴—X  (2)

In formula (2), R⁴ is a divalent hydrocarbon group of 1 to 10 carbonatoms. Examples of R⁴ include alkylene, arylene and alkenylene groupsand combinations thereof, such as methylene, ethylene, propylene,n-butylene, i-butylene, hexylene, decylene, phenylene, andmethylphenylethylene, and combinations thereof. Of these, propylene,hexylene and decylene are preferred, with hexylene being most preferred.X is a halogen atom such as Cl, Br or I.

Typical examples of the compound of formula (2) are given below.Cl—(CH₂)₃—ClCl—(CH₂)₆—ClCl—(CH₂)₁₀—ClBr—(CH₂)₆—BrBr—(CH₂)₁₀—Br

The polysulfide has the formula (3):M₂S_(n)  (3)wherein M is ammonium or an alkali metal and n is a positive numberhaving an average value of 2 to 6. Non-limiting examples of M includeNa, K, Cs, Li and NH₄, with Na being preferred. Examples of thepolysulfide having formula (3) include Na₂S_(n), K₂S_(n), Cs₂S_(n),Li₂S_(n), and (NH₄)₂S_(n), with Na₂S_(n) being preferred. Thepolysulfide may also take the form of a hydrate.

In the method of the present invention, a halogen-terminatedorganosilicon compound having formula (1), and optionally ahalogen-containing compound having formula (2) and/or sulfur are reactedwith an aqueous solution or dispersion of a sulfide having formula (3)or a hydrate thereof in the presence of a phase transfer catalyst. Onepreferred procedure of performing this reaction involves mixing thehalogen-terminated organosilicon compound having formula (1), an aqueoussolution or dispersion of the phase transfer catalyst and optionally thehalogen-containing compound having formula (2) and/or sulfur and thenadding an aqueous solution or dispersion of the polysulfide havingformula (3) or a hydrate thereof to the mixture for reaction. Thisprocedure allows for efficient production of the desired product,sulfide chain-bearing organosilicon compound having the averagecompositional formula (4).

Although the phase transfer catalyst is used in any desired amount, itmay be added in an amount of 0.1 to 10.0% by weight, preferably 0.5 to5.0% by weight, and more preferably 1.0 to 3.0% by weight, based on theweight of the compound of formula (1). Outside the range, less amountsof the catalyst may not be effective for the reaction to proceed rapidlywhereas too much amounts of the catalyst may adversely affect theperformance of the resultant organosilicon compound as a silica-loadedrubber additive.

The phase transfer catalyst may be premixed either with the compound offormula (1) or with an aqueous solution or dispersion of the polysulfideof formula (3) or hydrate thereof. The premixing with the compound offormula (1) is preferred because of quicker start of reaction.

When the phase transfer catalyst is mixed with the compound of formula(1), the phase transfer catalyst may be diluted with water. Fordilution, the amount of water added may be 0 to about 500% by weight,preferably about 100 to about 300% by weight based on the weight of thephase transfer catalyst. When water is added, it is acceptable to mixthe compound of formula (1) with the phase transfer catalyst and thenadd water to the mixture. In this embodiment, the amount of water addedis the same as above.

The polysulfide of formula (3) or hydrate thereof is used in aqueoussolution or water dispersion form. Although the amount of water added tothe polysulfide is not critical, water is preferably added in suchamounts that a total amount of water is 10 to 1000% by weight, morepreferably 30 to 300% by weight relative to the compound of formula (1)to be reacted with the polysulfide of formula (3). Outside the range,smaller amounts of water may allow the polysulfide or hydrate thereof toprecipitate, with the concomitant difficulty of dispersion, and largeramounts of water may enhance the susceptibility of the compound offormula (1) to hydrolysis.

An aqueous solution or dispersion of the polysulfide of formula (3) orhydrate thereof may be prepared by using hydrous sodium polysulfide, thereaction product of an anhydrous alkali metal with sulfur, or thereaction product of metallic sodium or potassium with sulfur, and addingany of these polysulfides or hydrates thereof to water.

With respect to the molar ratio of the compound of formula (1) to thepolysulfide of formula (3), it is a general practice to use the compoundof formula (1) in an equimolar amount to the M (ammonium or alkalimetal) of the polysulfide. It is understood that the system becomesalkaline as the moles of the compound of formula (1) is reduced, andbecomes nearly neutral as the moles of the compound of formula (1) isincreased. Specifically, the molar ratio of the compound of formula (1)to the polysulfide of formula (3) is preferably from 1.9 to 2.2, morepreferably from 2.0 to 2.1.

In the practice of the invention, sulfur is added if necessary. Whenused, the amount of sulfur added is determined so as to provide thedesired value of m in the average compositional formula (4) and is tomake up the shortage of sulfur if observed after the charge of thepolysulfide of formula (3): M₂S_(n). Sulfur need not be added in case ofn=m.

In an optional embodiment wherein the compound of formula (2) is added,further amounts of the polysulfide of formula (3) and optionally sulfurmay be added in accordance with the amount of the compound of formula(2) added. That is, the compounds of formulae (1) and (2) may be addedin such amounts that the total moles of the compounds of formulae (1)and (2) is essentially equimolar to the M of the polysulfide of formula(3): M₂S_(n). Specifically, the molar ratio of the compounds of formulae(1) and (2) to the polysulfide of formula (3) is preferably from 1.9 to2.2, more preferably from 2.0 to 2.1.

With respect to the molar ratio of the compound of formula (1) to thecompound of formula (2), 2 mol of the compound of formula (1) may becombined with 1 mol of the compound of formula (2) in order that q havean average value of 2, for example.

In preparing the compound of the invention, an organic solvent may ormay not be used. While a solventless system is preferred, it isacceptable to use a solvent having low water solubility. For example,use may be made of aliphatic hydrocarbons such as pentane, hexane,heptane and octane and aromatic hydrocarbons such as benzene, tolueneand xylene. When used, the amount of the solvent is not particularlylimited, but is preferably up to about 2 times the amount of thecompound of formula (1) and more preferably equal to or less than theamount of the compound of formula (1).

Although the reaction temperature is not critical, it is generally fromroom temperature to about 200° C., preferably about 40 to about 170° C.,more preferably about 50 to about 100° C. The reaction time is generally30 minutes or more, and the reaction proceeds to completion within about1 hour to about 15 hours.

At the end of reaction, the reaction mixture is subjected to separatoryoperation so that it is separated into the desired compound layer andthe water layer. If a salt has precipitated in the reaction mixture,water may be added to dissolve the salt, or filtration be made beforeand/or after the separation. Where a solvent is used, it may bedistilled off in a partial vacuum after the separation.

To remove water from the desired compound, water may be distilled off ina partial vacuum after the separation. Alternatively, after the waterlayer is separated off, a desiccant is added to the desired compound fordrying. Exemplary desiccants are sodium sulfate and magnesium sulfate.

The desired compound that is prepared by the inventive method has theaverage compositional formula (4).(R¹O)_((3-p))(R²)_(p)Si—R³—S—(R⁴—S_(m))_(q)—R⁴—S—R³—Si(OR¹)_((3-p))(R²)_(p)  (4)

In the formula, R¹ and R² each are a monovalent hydrocarbon group of 1to 4 carbon atoms, R³ and R⁴ each are a divalent hydrocarbon group of 1to 10 carbon atoms, m is a positive number having an average value of 2to 6, p is 0, 1 or 2, and q is 1, 2 or 3, preferably 1 or 2. R¹ to R⁴are as exemplified above for formula (1). The subscript m is a positivenumber having an average value of 2 to 6, preferably 2 to 4, morepreferably 2 to 3.

Typical examples of the compound of formula (4) are given below whereinm and q are numbers having average values as described above.(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₃—S_(m)—(CH₂)₃—S—(CH₂)₃—Si(OCH₃)₃(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(m)—(CH₂)₆—S—(CH₂)₃—Si(OCH₃)₃(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₁₀—S_(m)—(CH₂)₁₀—S—(CH₂)₃—Si(OCH₃)₃(CH₃O)₃Si—(CH₂)₆—S—(CH₂)₆—S_(m)—(CH₂)₆—S—(CH₂)₆—Si(OCH₃)₃(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(m—(CH) ₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃(CH₃CH₂O)₃Si—(CH₂)₃—S—[(CH₂)₆—S_(m)]_(q)—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃

The sulfide chain-bearing organosilicon compounds of the averagecompositional formula (4) obtained by the method of the invention finduse as rubber compounding additives, especially in silica-loaded rubbercompositions for tire and similar applications.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation.

Synthesis Example 1

A 1-liter separable flask equipped with a nitrogen gas inlet,thermometer, Dimroth condenser and dropping funnel was charged with 250g of deionized water, 48 g (1.5 mol) of sulfur, and 132.0 g (1.0 mol) offlake sodium sulfide having a sodium sulfide content of 59 wt %. Thecontents were stirred for one hour at 50° C., yielding 430 g of anaqueous solution of polysulfide having the average composition:Na₂S_(2.5).

Example 1

A 1-liter separable flask equipped with a nitrogen gas inlet,thermometer, Dimroth condenser and dropping funnel was charged with142.6 g (0.4 mol) of 6-chlorohexylthiopropyl-triethoxysilane and 9.6 g(0.3 mol) of sulfur and heated at 80° C. To the flask was added anaqueous solution of 2.1 g of tetra-n-butylammonium bromide in 6.0 g ofdeionized water. Then 86 g (0.2 mol calculated as Na₂S_(2.5)) of anaqueous solution of the average composition: Na₂S_(2.5) obtained inSynthesis Example 1 was slowly added dropwise so as to keep atemperature of 80-90° C. The time taken for dropwise addition was 20minutes. After the completion of dropwise addition, the reaction mixturewas held for 5 hours for ripening. Thereafter, the reaction mixture wascooled below 40° C., combined with 100 g of toluene, and filtered. Thereaction liquid as filtered separated into upper and lower layers. Thelower layer was an aqueous solution in which NaCl formed was dissolved.The upper layer was concentrated under a partial vacuum to remove thetoluene, leaving 147.5 g of a red brown clear liquid. The liquid had aviscosity of 48.5 mm²/s, a refractive index of 1.5074, and a specificgravity of 1.072 at 25° C.

On analysis by infrared (IR) absorption spectroscopy, proton nuclearmagnetic resonance (¹H-NMR) spectroscopy, gel permeation chromatography(GPC), supercritical chromatography, and sulfur content determination,it was confirmed to be a sulfide group-bearing alkoxysilane of thefollowing average compositional formula.(CH₃CH₂O)₃Si(CH₂)₃—S—(CH₂)₆—S₄—(CH₂)₆—S—(CH₂)₃Si(OCH₂CH₃)₃

Example 2

A 1-liter separable flask equipped with a nitrogen gas inlet,thermometer, Dimroth condenser and dropping funnel was charged with142.6 g (0.4 mol) of 6-chlorohexylthiopropyl-triethoxysilane and heatedat 80° C. To the flask was added an aqueous solution of 2.1 g oftetra-n-butylammonium bromide in 6.0 g of deionized water. Then 86 g(0.2 mol calculated as Na₂S_(2.5)) of an aqueous solution of the averagecomposition: Na₂S_(2.5) obtained in Synthesis Example 1 was slowly addeddropwise so as to keep a temperature of 80-90° C. The time taken fordropwise addition was 20 minutes. After the completion of dropwiseaddition, the reaction mixture was held for 5 hours for ripening.Thereafter, the reaction mixture was cooled below 40° C., combined with100 g of toluene, and filtered. The reaction liquid as filteredseparated into upper and lower layers. The lower layer was an aqueoussolution in which NaCl formed was dissolved. The upper layer wasconcentrated under a partial vacuum to remove the toluene, leaving 136.3g of a red brown clear liquid. The liquid had a viscosity of 44.2 mm²/s,a refractive index of 1.4906, and a specific gravity of 1.044 at 25° C.

On analysis by IR spectroscopy, ¹H-NMR spectroscopy, GPC, supercriticalchromatography, and sulfur content determination, it was confirmed to bea sulfide group-bearing alkoxysilane of the following averagecompositional formula.(CH₃CH₂O)₃Si(CH₂)₃—S—(CH₂)₆—S_(2.5)—(CH₂)₆—S—(CH₂)₃Si(OCH₂CH₃)₃

Example 3

A 1-liter separable flask equipped with a nitrogen gas inlet,thermometer, Dimroth condenser and dropping funnel was charged with142.6 g (0.4 mol) of 6-chlorohexylthiopropyl-triethoxysilane, 31.0 g(0.2 mol) of 1,6-dichlorohexane, and 19.2 g (0.6 mol) of sulfur andheated at 80° C. To the flask was added an aqueous solution of 4.2 g oftetra-n-butyl-ammonium bromide in 10.0 g of deionized water. Then 172 g(0.4 mol calculated as Na₂S_(2.5)) of an aqueous solution of the averagecomposition: Na₂S_(2.5) obtained in Synthesis Example 1 was slowly addeddropwise so as to keep a temperature of 80-90° C. The time taken fordropwise addition was 30 minutes. After the completion of dropwiseaddition, the reaction mixture was held for 5 hours for ripening.Thereafter, the reaction mixture was cooled below 40° C., combined with200 g of toluene, and filtered. The reaction liquid as filteredseparated into upper and lower layers. The lower layer was an aqueoussolution in which NaCl formed was dissolved. The upper layer wasconcentrated under a partial vacuum to remove the toluene, leaving 168.2g of a red brown clear liquid. The liquid had a viscosity of 144 mm²/s,a refractive index of 1.5358, and a specific gravity of 1.112 at 25° C.

On analysis by IR spectroscopy, ¹H-NMR spectroscopy, GPC, supercriticalchromatography, and sulfur content determination, it was confirmed to bea sulfide group-bearing alkoxysilane of the following averagecompositional formula.(CH₃CH₂O)₃Si(CH₂)₃—S—(CH₂)₆—S₄—(CH₂)₆—S₄—(CH₂)₆—S—(CH₂)₃Si(OCH₂CH₃)₃

Example 4

A 1-liter separable flask equipped with a nitrogen gas inlet,thermometer, Dimroth condenser and dropping funnel was charged with142.6 g (0.4 mol) of 6-chlorohexylthiopropyl-triethoxysilane and 31.0 g(0.2 mol) of 1,6-dichlorohexane and heated at 80° C. To the flask wasadded an aqueous solution of 4.2 g of tetra-n-butylammonium bromide in10.0 g of deionized water. Then 172 g (0.4 mol calculated as Na₂S_(2.5))of an aqueous solution of the average composition: Na₂S_(2.5) obtainedin Synthesis Example 1 was slowly added dropwise so as to keep atemperature of 80-90° C. The time taken for dropwise addition was 30minutes. After the completion of dropwise addition, the reaction mixturewas held for 5 hours for ripening. Thereafter, the reaction mixture wascooled below 40° C., combined with 200 g of toluene, and filtered. Thereaction liquid as filtered separated into upper and lower layers. Thelower layer was an aqueous solution in which NaCl formed was dissolved.The upper layer was concentrated under a partial vacuum to remove thetoluene, leaving 155.8 g of a red brown clear liquid. The liquid had aviscosity of 108 mm²/s, a refractive index of 1.5114, and a specificgravity of 1.071 at 25° C.

On analysis by IR spectroscopy, ¹H-NMR spectroscopy, GPC, supercriticalchromatography, and sulfur content determination, it was confirmed to bea sulfide group-bearing alkoxysilane of the following averagecompositional formula.(CH₃CH₂O)₃Si(CH₂)₃—S—(CH₂)₆—S_(2.5)—(CH₂)₆—S_(2.5)—(CH₂)₆—S—(CH₂)₃Si(OCH₂CH₃)₃

Japanese Patent Application No. 2005-285868 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A method for preparing a sulfide chain-bearing organosilicon compoundhaving the average compositional formula (4):(R¹O)_((3-p))(R²)_(p)Si—R³—S—(R⁴—S_(m))_(q)—R⁴—S—R³—Si(OR¹)_((3-p))(R²)_(p)  (4)wherein R¹ and R² each are a monovalent hydrocarbon group of 1 to 4carbon atoms, R³ and R⁴ each are a divalent hydrocarbon group of 1 to 10carbon atoms, m is a positive number having an average value of 2 to 6,p is 0, 1 or 2, and q is 1, 2 or 3, the method comprising the step ofreacting: (a) a halogen-terminated organosilicon compound having thegeneral formula (1):(R¹O)_((3-p))(R²)_(p)Si—R³—S—R⁴—X  (1) wherein R¹ and R² each are amonovalent hydrocarbon group of 1 to 4 carbon atoms, R³ and R⁴ each area divalent hydrocarbon group of 1 to 10 carbon atoms, X is a halogenatom, and p is 0, 1 or 2, and optionally (b) a halogen-containingcompound having the general formula (2):X—R⁴—X  (2) wherein R⁴ is a divalent hydrocarbon group of 1 to 10 carbonatoms and X is a halogen atom, and/or (c) sulfur with (d) an aqueoussolution or dispersion of a polysulfide having the formula (3):M₂S_(n)  (3) wherein M is ammonium or an alkali metal and n is apositive number having an average value of 2 to 6 or a hydrate thereofin the presence of (e) a phase transfer catalyst.
 2. The method of claim1 wherein the halogen-terminated organosilicon compound of formula (1),an aqueous solution or dispersion of the phase transfer catalyst, andoptionally the halogen-containing compound of formula (2) and/or sulfurare mixed prior to the reaction with an aqueous solution or dispersionof the polysulfide of formula (3) or hydrate thereof.
 3. The method ofclaim 1 wherein in the average compositional formula (4), m is apositive number having an average value of 2 to
 3. 4. The method ofclaim 1, which comprises reacting: (a)6-chlorohexylthiopropyltriethoxysilane; (c) sulfur; (d) Na₂S_(2.5); and(e) tetra-n-butylammonium bromide to prepare(CH₃CH₂O)₃Si(CH₂)₃—S—(CH₂)₆—S₄—(CH₂)₆—S—(CH₂)₃Si(OCH₂CH₃)₃.
 5. Themethod of claim 1, which comprises reacting: (a)6-chlorohexylthiopropyltriethoxysilane; (b) 1,6-dichlorohexane; (c)sulfur; (d) Na₂S_(2.5); and (e) tetra-n-butylammonium bromide to prepare(CH₃CH₂O)₃Si(CH₂)₃—S—(CH₂)₆—S₄—(CH₂)₆—S₄—(CH₂)₆—S—(CH₂)₃Si(OCH₂CH₃)₃. 6.A method in accordance with claim 1 for preparing a sulfidechain-bearing organosilicon compound having the average compositionalformula (4):(R¹O)_((3-p))(R²)_(p)Si—R³—S—(R⁴—S_(m))_(q)—R⁴—S—R³—Si(OR¹)_((3-p))(R²)_(p)  (4)wherein R¹ and R² each are a monovalent hydrocarbon group of 1 to 4carbon atoms, R³ and R⁴ each are a divalent hydrocarbon group of 1 to 10carbon atoms, m is a positive number having an average value of 2 to 6,p is 0, 1 or 2, and q is 1, 2 or 3, said method comprising the step ofreacting: (a) a halogen-terminated organosilicon compound selected fromthe group consisting of (CH₃O)₃Si—(CH₂)₃—S—(CH₂)₃—Cl,(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₆—Cl, (CH₃O)₃Si—(CH₂)₃—S—(CH₂)₈—Cl,(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₁₀—Cl, (CH₃O)₃Si—(CH₂)₃—S—(CH₂)₆—Br,(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₃—Cl, (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—Cl,(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₈—Cl, (CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₁₀—Cl,(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—Br, and(CH₃CH₂O)₃Si—CH₂CH(CH₃)CH₂—S—(CH₂)₆—Cl, and optionally (b) ahalogen-containing compound selected from the group consisting ofCl—(CH₂)₃—Cl, Cl—(CH₂)₆—Cl, Cl—(CH₂)₁₀—Cl, Br—(CH₂)₆—Br, andBr—(CH₂)₁₀—Br, and/or (c) sulfur with (d) an aqueous solution ordispersion of a polysulfide selected from the group consisting ofNa₂S_(n), K₂S_(n), Cs₂S_(n), Li₂S_(n), and (NH₄)₂S_(n) in the presenceof (e) a phase transfer catalyst selected from the group consisting oftetrabutylammonium bromide, tetrabutylammionium chloride,tetramethylammonium bromide, tetramethylammonium chloride,tetraethylammonium bromide, tetraethylammonium chloride,tetrabutylammonium phosphate, tetrabutylammonium phosphite,tetrabutylammonium sulfate, tetrabutylammonium fluoride,benzyltrimethylammonium bromide, and tetraphenylammonium bromide.
 7. Themethod of claim 1, wherein n=m and wherein no sulfur is added in thereaction.
 8. The method of claim 1, wherein the compound of formula (4)is selected from the group consisting of(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₃—S_(m)—(CH₂)₃—S—(CH₂)₃—Si(OCH₃)₃,(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(m)—(CH₂)₆—S—(CH₂)₃—Si(OCH₃)₃,(CH₃O)₃Si—(CH₂)₃—S—(CH₂)₁₀—S_(m)—(CH₂)₁₀—S—(CH₂)₃—Si(OCH₃)₃,(CH₃O)₃Si—(CH₂)₆—S—(CH₂)₆—S_(m)—(CH₂)₆—S—(CH₂)₆—Si(OCH₃)₃,(CH₃CH₂O)₃Si—(CH₂)₃—S—(CH₂)₆—S_(m)—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃, and(CH₃CH₂O)₃Si—(CH₂)₃—S—[(CH₂)₆—S_(m)]_(q)—(CH₂)₆—S—(CH₂)₃—Si(OCH₂CH₃)₃.